FACE AND BYPASS AHU APPLICATION 4

[sfcontrols]

Hello,

I need your help with the following:
I'm involved in a Hospital project where the disigner has especified a dedicated ahu's for each OR's..without any
any reheat...at this stage of the project provide hot water or electrical reheat is almost impossible. I was thinking to provide ahus with face and by pass.
Would be a good solution to use face and bypass ahu for this aplication. The project is in south america.
Thanks,

 

[simsd]

It's been many years since I looked at the set up of these but let me ask a few questions. The type I was familiar was in a cold climate.They had a steam coil that ran full out in the winter and controlled the discharge air with the face and bypass dampers. As the temperature in the duct rose, the face damper would start to close and bypass the coil. Is this similar to what you want to do except in a cooling application?

What are you thinking?

Can you describe it more in depth please?

 

[Vellum]

You will run into a problem with humidity if you by-pass the cooling coil while in the cooling mode. This would not be good IMO. Is the coil DX or chilled water?

 

[absrbrtek]

You will have a problem with humidity along with keeping stable temperatures. Face and bypass has to be the worst way to maintain constant temperature in a room. I surely wouldn't want it in an OR setting. JMHO

 

[sfcontrols]

Thank you all for your help

It's a chilled water system...
Now I have second question...will a heat pipe system work for this application..do you have any experience...
Thank you again.

 

[atlas06]

why is it that electric reheat is impossible in a hospital?
Everything is possoble. When there is a will, there is a way (even in south america). Reheat for an OR is your only bet in my opinion.
If you have a pre-heat coil, you should be able to get reheat, don't you? heck, you can actually power your electric reheat from the emergency generator if you have to.
Could you elaborate on your situation a little more? weather data, room temp, ACH requirements, design criteria, what are your available utility sources? etc..

 

[simsd]

I can't believe this is for an OR. What's wrong with these people? Look peoples lives can be at stake here. Let's do it right or not do it at all.

 

[Vellum]

What about adding electric Pre-heat to the units or adding a dedicated oa unit that supplies OA to all the OR units. Simsd is right, what is the cost of one life because of an improperly designed system?

 

[marcoh]

Are you proposing to have 100% cooling at all times and bypass the coil to control temperature? Why not install control valves in the chilled water pipework to each coil?